The US is in talks with Vietnam to place military equipment in the country for the first time since the end of the Vietnam War just over forty years ago, according to US officials.

The US and Vietnamese governments have been discussing the use of Da Nang as a site to store military equipment that could purportedly be used to respond to natural disasters in the region.

The coastal city, perched strategically on the Southeast Asia Sea, is where US combat forces first arrived in Vietnam in 1965.

The talks about pre-positioning equipment have more symbolic significance. The two former enemies share anxiety about a rising China, making them partners over the past two decades.

Beijing, however, accuses Washington of meddling in the regional issues and deliberately stirring up tensions in the South China Sea.

China claims nearly all of the Southeast Asia Sea, despite partial counterclaims by Brunei, Malaysia, Taiwan, Vietnam and the Philippines. China is also locked in disputes with Japan and South Korea over the East Asia Sea.

US President Barack Obama will arrive in Hanoi on Sunday for a three-day visit that will anoint Vietnam, a one-party communist state, as an essential part of his “pivot” towards Asia.

The Obama administration had hoped to announce the end of an embargo on selling offensive weapons to Vietnam, which would be another symbolic step in normalizing relations, before Obama’s visit.

But the cautious nature of the military engagements between Washington and Hanoi, which include limits on the number of port visits and a stress on humanitarian missions, underlines the sensitivities that surround any US involvement in Vietnam.

The US carried out an eight-year military intervention in the country from 1965-73.

While Vietnam wants to work with the US to challenge China’s expansive territorial claims on the Southeast Asia Sea, it is concerned about irritating its powerful neighbor, a fellow Communist-run state with which Vietnam shares a complex set of security, trade and political ties.

Hanoi has a complicated past with Beijing, which controlled much of northern Vietnam for centuries.

“As a Communist party, the US and its values pose an existential threat to [Vietnam’s] regime — but China poses an existential threat to the future of Vietnam as a country,” says Marvin Ott, a Southeast Asia expert at the Johns Hopkins School of Advanced International Studies in Washington.

“They have 2000 years of dealing with a China problem and they are better at managing it than anyone else,” Ott said.

Across Southeast Asia, concerns about China and its growing military have created an opportunity for the US to improve relationships.

In recent years, American aircraft and ships have returned to the Philippines for the first time in more than two decades, while US Marines have started training in Australia and new guidelines have allowed for closer cooperation with Japan.

Vietnam has also requested US assistance, albeit at a slower pace.

“Vietnam is going to be very cautious about not crossing red lines with China and the United States is going to respect that,” said Patrick Cronin, Asia director at the Center for a New American Security. “We are not looking for any new bases.”